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The numerous closely spaced scutes combined with the lack of incurrent siphon tentacles has me puzzled. The mantle is pushing me toward thinking I've accidentally bought a gigas but I am by no means a clam expert...

I could be very wrong (so don't get discouraged until you hear from others or research a little more),but the Clam looks a little stressed to me. Overall, it looks great, but it looks like it might be beginning to gape a bit. Thus the lack of the filaments that you are searching for. Google image search "gaping reef clam" and you will see that the filaments are retracted due to the stretching.

Like I said, I could be wrong. But when I saw the original picture, my first thought was, "It looks like it's gaping". Just keep an eye on it and good luck!

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I will try on the photo, but it's attached pretty well now and I'm less likely to move it. I'll see what I can do. I'll also get some more top down shots. It could have been gaping in those photos certainly, it was in the tank 48 hours at that point. I appreciate the info, I'm not trying to be argumentative on the ID by requesting reasons, just trying to grow my own knowledge as I would like to successfully keep clams and be able to identify them.

I will try on the photo, but it's attached pretty well now and I'm less likely to move it. I'll see what I can do. I'll also get some more top down shots. It could have been gaping in those photos certainly, it was in the tank 48 hours at that point. I appreciate the info, I'm not trying to be argumentative on the ID by requesting reasons, just trying to grow my own knowledge as I would like to successfully keep clams and be able to identify them.

if you want to read up on clams more and understand them better, i would highly recommend these 2 books :

Giant Clams by Daniel Knop
Giant Clams in the Sea and the Aquarium by James Fatheree

they are great reads and provide a great source of information about clams. I bought my copies used from Amazon (they may actually be out of print).

That's a crocea. 100% not a derasa. Almost any clam can have scutes too. In the wild a crocea is a boring clam that recesses itself into the reef rock and wears its scutes off. In a reef tank I have had 5 or 6 that had a shell identical to that.

That's a crocea. 100% not a derasa. Almost any clam can have scutes too. In the wild a crocea is a boring clam that recesses itself into the reef rock and wears its scutes off. In a reef tank I have had 5 or 6 that had a shell identical to that.

Here are a few new ones from the front. Excuse the particulates in the water I was scraping the glass when I noticed the flow was raising the skirt so to speak which gave a good opportunity to see some growth. I would normally focus stack a set like this but I don't really have time. I'll try to snag a few top downs later as well before the LED's turn off.